It might just be marketing?
Get sellers hooked on the 'good' bits first -- reveal the 'bad' bits later. Like, a few down the line, reduce the max. number to 50, a few more then down to 30 items. But who knows?
I now find it impossible to even guess at the true number of listings, even in a niche area like Art Deco Glass.
When I first started selling, that search (UK Only) would return about 18K results. Over the years that went down to just about 10K. It was obvious that on an offer week-end the results went up by hundreds of extras. But that declined probably as sellers realised that even if they listed all day, any 'extra' sales were few and not worth the effort. (Which probably supports your view)
The last few times when I could roughly work out how many extra listings there were, before ebay started seriously messing-up the search by only searching some 'fruitful' categories instead of All Categories, then profiling my buying habits, then 'Stream-lining', then by adding in all manner of Related Sponsored Listings, the total barely increased at all on Offer Week-Ends.
Now it's impossible to even guess how many genuine items there are on ebay. The old categories are gone, the new ones so huge that the same search will start with 30K+ results and depending on how many filters you apply and in what order, you can get any total you like. But, guesstimating from sales over the next week or so (or lack of any noticeable increase), I don't think there is any 'flood' of new listings. At least not in that particular niche.
I agree with you in thinking that "...not many real private sellers promote listings...". But because they don't, their ads. don't get seen and their sales are reduced, so they stop wasting their time listing stuff that never sells. It's one of the reasons they're not selling here any more.
